Electronic mail is becoming an increasingly popular form of communications. Electronic mail systems allow one user of a computer system (i.e., a sender) to send a message electronically to another user (i.e., a recipient). To create an electronic mail message, the sender designates the recipient to whom the electronic mail is to be sent and creates the body (e.g., text) of the electronic mail message. The electronic mail system then forwards the electronic mail message to the recipient via a communications mechanism such as a local area network or the Internet. When the recipient receives the electronic mail messages, the recipient can view the body of the electronic mail message.
To ensure format compatibility among various electronic mail systems, the electronic mail messages are formatted in accordance with a conventional format such as defined by the Simple Mail Transfer Protocol ("SMTP"). According to this format, the electronic mail message contains an envelope portion and a body portion. The envelope portion identifies the sender and the recipient, identifies the electronic mail address of the recipient, and may identify the subject of the electronic mail message. The body portion contains the message itself, which is typically in text format. The electronic mail system may need to route an electronic mail message through various computer systems until it reaches the computer system of the recipient. Each of the computer systems through which the electronic mail message is routed use the recipient's electronic mail address to forward the electronic mail message.
Electronic mail systems store electronic mail messages that have been sent or received in a file referred to as the electronic mail file. The electronic mail files are typically organized into various folders and subfolders. The folders allow a user of the electronic mail system to store related electronic mail messages in the same folder in a way that is very similar to how directories allow a user of a file system to store related files in the same directory. When the electronic mail system receives an electronic mail message for a user, the electronic mail system stores the electronic mail message in a folder that is designated as the "Inbox" folder within the user's electronic mail file. The electronic mail system allows the user to view the electronic mail messages that are currently in the Inbox folder. When the user selects to display the contents of the Inbox folder, the electronic mail system displays information from the envelope portion (e.g., sender's name and subject information) for each of the electronic mail messages currently in the folder. Based on the envelope information, the user can select to display the body of an electronic mail message. The electronic mail system also allows the user to move the electronic mail messages from the Inbox folder to other folders or to delete the electronic mail messages. When a user sends an electronic mail message, the electronic mail system typically saves a copy of the electronic mail message in a folder that is designated as the "Sent" folder. The user can move and delete the electronic mail messages stored in any of the folders in the same manner as done for the Inbox folder.
The electronic mail address for a user uniquely identifies the computer system at which the recipient expects to receive the electronic mail messages. Electronic mail addresses can be very complex strings of characters that identify countries, companies, divisions within companies, and individual users. Thus, to provide a more friendly user interface, typical electronic mail systems maintain an address book that contains a mapping of the names of the users to their electronic mail addresses. Thus, when a user wishes to designate a recipient, the user need only indicate the name of the recipient and the electronic mail system uses the address book to retrieve the electronic mail address for that recipient. A user will generally have a personal address book with the names and electronic mail addresses of those recipients to whom the user normally sends electronic mail messages. In addition, the electronic mail systems typically maintain a global address book that is shared by all users of the electronic mail system. For example, the global address book may contain the names and electronic mail addresses of all the employees of a company. An employee may then store the names and electronic mail addresses of non-employee friends in the employee's own personal address book. When the electronic mail system sends an electronic mail message, it searches the global and personal address books for the electronic mail address of the recipient.
Prior to the popularity of the Internet, a user of an electronic mail system generally received electronic mail messages only from known senders. For example, an employee of a company would receive electronic mail messages only from other employees of the company. The electronic mail system may only be connected to computer systems owned by the company. However, with the increasing popularity of the Internet, a user may be able to send electronic mail messages to anyone who is connected to the Internet. The sender of an electronic mail message needs only to know the electronic mail address of the recipient. Thus, users can and often do receive electronic mail messages from unknown senders.
Recently, a problem has developed which seriously impairs the effectiveness of electronic mail systems. Many large promotional companies are turning to the Internet to advertise products of their clients. These promotional companies acquire and maintain lists of electronic mail addresses for thousands of users. When a client wants to advertise a product, the promotional company will send an electronic mail message to each electronic mail address in its list. A user may occasionally receive an unsolicited electronic mail message from such a promotional company. Such occasional receipt of such electronic mail message, while annoying, does not seriously impair the effectiveness of the electronic mail system. However, because of the perceived benefits of advertising via the Internet, a user may now receive so many unsolicited electronic mail messages on a daily basis, that the unsolicited electronic mail messages vastly outnumber the electronic mails messages received from known senders. The process of sending these promotional electronic mail messages indiscriminately to the various electronic mail addresses by the promotional companies is referred to as "spamming." Because a recipient may receive so many unsolicited (i.e., junk) electronic mail messages, it may be very difficult for the recipient to sort through and determine which electronic mail messages are not junk. Such sorting has been a serious impediment to the effectiveness of the electronic mail systems. The seriousness of the problem has been recognized and legislation has even been proposed that would outlaw such spamming practices. In addition, several litigations have been spawned to force such promotional companies to cease their spamming practices.
One potential solution to the problems resulting from the spamming practices has been tried, but unfortunately has been unsuccessful. A service, known as a "de-spamming service," has been provided that attempts to limit the junk mail that is sent. Such a de-spamming service maintains a list of the electronic mail addresses of users who have requested not to receive junk mail. When a promotional company wishes to send an electronic mail message to all the users whose electronic mail addresses are on its mailing list, the promotional company first sends the electronic mail messages to the de-spamming computer system. The de-spamming computer system checks its list of electronic mail addresses and deletes any of the electronic mail messages that are destined to any electronic mail addresses on its list. The de-spamming computer system then forwards the remaining electronic mail messages onto the recipients. Whenever a recipient does not want to be included on a mailing list, the recipient can notify the de-spamming computer system, which will add the recipient's electronic mail address to the list of electronic mail addresses that are not to receive junk mail. Recently, however, such de-spamming services have ceased offering the service because it has proved to be uneconomical.
Certain electronic mail systems also allow a user to designate how to automatically handle a received electronic mail message. For example, a user can indicate that all electronic mail messages received from a certain sender can automatically be stored in a designated folder, be deleted, or be forwarded to another recipient. To provide such routing of electronic mail messages, the user needs to specify a characteristic (e.g., sender=John Smith) of the envelope portion or the body portion so that the electronic mail system can determine which electronic mail systems satisfy the characteristic. However, with such electronic mail systems, a user cannot specify how to automatically handle electronic mail messages if they are unaware of any characteristic of the electronic mail message. In particular, a user may not know in advance the identity of the sender of junk mail and thus cannot have the junk mail automatically deleted.